Coupling mechanism between cyclic loading damage evolution and hydrogen permeation in impure rock salt

Damage evolution and seepage behavior variations of rock salt under cyclic loading directly affect the long-term safety of the storage, especially the unclear damage-permeation coupling mechanism of impure rock salt. Through cyclic loading and hydrogen permeation tests, this study systematically investigated the damage evolution and permeability change patterns of impurity rock salt under different stress levels and cycle counts. Results show that the damage evolution presents the stage characteristics of “initial intense damage-gradual stable damage-final rapid damage”. High stress promotes the development of shear cracks and significantly increases the cumulative acoustic emission energy. Permeability increases nonlinearly with stress level and cycle number. Stress level determines the type of damage mechanism, while cycle number determines the degree of damage accumulation. And shear crack penetration is the main controlling factor for the formation of seepage channels. A permeability prediction model based on cumulative acoustic emission energy is established, enabling effective characterization of the damage-permeation coupling relationship. The research provides important theoretical basis for the sealing integrity and safe operation of salt cavern hydrogen storage.